﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Weibo.Common
{
    public class UrlShort
    {
        public static string[] ShortUrl(string url)
        {
            //可以自定义生成MD5加密字符传前的混合KEY
            string key = "17desk";
            //要使用生成URL的字符
            string[] chars = new string[]{
 		"a","b","c","d","e","f","g","h",
     	"i","j","k","l","m","n","o","p",
		"q","r","s","t","u","v","w","x",
   		"y","z","0","1","2","3","4","5",
 		"6","7","8","9","A","B","C","D",
  		"E","F","G","H","I","J","K","L",
  		"M","N","O","P","Q","R","S","T",
		"U","V","W","X","Y","Z"
	};

            //对传入网址进行MD5加密
            string hex = System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(key + url, "md5");

            string[] resUrl = new string[4];

            for (int i = 0; i < 4; i++)
            {
                //把加密字符按照8位一组16进制与0x3FFFFFFF进行位与运算
                int hexint = 0x3FFFFFFF & Convert.ToInt32("0x" + hex.Substring(i * 8, 8), 16);
                string outChars = string.Empty;
                for (int j = 0; j < 6; j++)
                {
                    //把得到的值与0x0000003D进行位与运算，取得字符数组chars索引
                    int index = 0x0000003D & hexint;
                    //把取得的字符相加
                    outChars += chars[index];
                    //每次循环按位右移5位
                    hexint = hexint >> 5;
                }
                //把字符串存入对应索引的输出数组
                resUrl[i] = outChars;
            }
            return resUrl;
        }
    }
}
